This invention relates in general to systems that monitor parameters in industrial processes for parameter values that are outside of the desired norm, and in particular to systems that monitor pressure vessels for over pressure or under pressure situations, and to equipment that is to be used in connection with devices that automatically shut down a process when an over pressure or under pressure situation could threaten to rupture or collapse the pressure vessel.
Industrial operations, particularly those that include pressure sensitive operations, often require devices that monitor pressure vessels for over pressure or under pressure situations. These monitors are connected to devices which may automatically shut down the industrial process in an over or under pressure situation. One of the problems with these systems is the inability to know if the monitoring system is actually functioning. For example, process materials may clog a sensing port, or otherwise prevent the pressure sensing device from properly monitoring system pressure. In instances where the monitoring system is relied upon to cause the emergency shut down of the process, it is critical that the system either function with 100% reliability, or that the system somehow alert the operator of the facility that it is not working properly, so that it call be repaired. Engineers have improved the reliability of critical shutdown system components in order to improve the level of safety of a production process. However, while the reliability of monitoring systems has improved, they still are not 100% reliable. Furthermore, it would be foolish to assume that a given system is 100% reliable, given the dangerous consequences of vessel failure in an industrial process. Accordingly, it is most important to know when a monitoring system has failed.